Switching mechanism for multiple frequency band receivers



March 24, 1942., w A, SCHAPER ErAL 2,277,149

SWITCHING MECHANISM FR MULTIXLE FREQUENCY BAND RECEIVER Y' Filed April8, 1940 2 Sheets-Sheety 2 INVENTUM l WILLIAM A, 5CH/WEF; BY QEORQE B.MaGW-:LLM

Patented Mar. 24, 1 942 SWITCHIG MECHANISM FOR MULTIPLE FREQUENCY BANDBECEIVERS William A. Schaper, Cicero, and George B. Mc- Clellan,Chicago, Ill., assignors to Johnson Laboratories, Inc., IllinoisChicago, Ill., a corporation of Application April s, i940, serial No.328,458

(o1. zoo- 11) 4 Claims.

- 'Ihis invention relates `to switching mechanism for radioreceivers,vsuch as those used for'the reception of broadcasting, andmore particularly to receivers intended to cover a very wide range offrequencies, or plural bands extending over the important portions ofsuch a wide range.

The invention provides means by which the very considerable advantagesof permeability tuning may be secured in such wide band receivers.

The switching arrangements which'we employ with our novel coil systemare different from..

although not necessarily more complicated than,

those employed inA systems in which separate inductive windings areemployed for each wave band. These switching arrangements, together withsuch modications thereof as will readily occur to those skilled in theart, taken in connection with the coil system per se constitute thenovel structure which when employed with other components already wellknown, to form variably tunable resonant circuits, makes possible theproduction of highly enicient permeabilityf tuned plural-hand wide-rangeradio receivers in accordance with the invention.

In order that the principle underlying our invention may be properlyunderstood, we shall first describe a coil system which provides fourdifferent air-core inductance values, and we shall then show how thiscoil system, `or modiiications thereof, may be employed in practicalreceivers, reference being had to the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a type of winding inaccordance .with thevinvention, suitable for providing four diierent.'aircore inductance values;

Fig. 2 is a diagram showing a switching method in accordance with theinvention, suitable for employment with the winding of Fig. 1;

Fig. 3 is a side elevation of a coil structure having a winding such asthat of Fig. l and a portion of the switch gear of Fig. 2;

asingle nat layer upon a suitable tube. In the ligure, the lower ends ofthese eight windings are numbered 1 to 8 respectively, the correspondingvupper ends being numbered 1' to 8' respectively, this same notationbeing used in "Figs, 2, 3, 4 and 6. It is preferable that the windingsbe spaced from each other by a distance` approximately equal to thediameter oi the conductive portion of the `wire employed. which may beeither solid 4wire or conductor having plural insulated strands. In Fig.l. for clarity, the ends oi the eight windings are shown as all leavingthe form or tube at the same angular point, but it will be understoodthat they are preferably brought oil at eight equiangularly spacedpoints.

Theeight windings of Fig. 1 may be made to produce numerous inductancevalues by. connecting them in various series, parallel, and

series parallel arrangements.

Fig. 2 shows the eiglit windings of Fig. 1 connected in four differentways, indicated by the letters a,'b, c and d. -End i of the lirstwinding is one terminal of the inductor, and end 8' of the eighthwinding is the other terminal of the inductor. For convenience ofexplanation, end I is shown as connected to a bus 9, and end 8 is shownconnected to a bus I0, and the remaining terminals are each shown asconnected to switch arms by which they may be connected either to a bus,or to the opposite end of the next adjacent winding. l

Maximum inductance .is secured by placing the eighijl windings in seriesaiding relation, as

. shown in Fig. 2a, by connecting the upper end A of each windingto thelower end of the next Fig. 4 is an end view of the coil structure lofFig. 3:

Fig. 5 is a schematic diagram of a receiver embodying the invention; andFigs. 6 and '1 are an elevation and a section on the line 1--1 of theelevation, respectively, oi a switching arrangement to carry out thechanges diagrammatically indicated in Fig. 2.

Figure 1 shows a construction which is suitable forv use with ourinvention with a coil sys- Y i Vtem in the-case in which four differentinductance values are to be provided.' Thecoilcomprises eight windingsarranged spirally side by side in adjacent winding.y To secure the nextlower value of inductance, the windings are thrown into two groups eachhaving four windings in series. This is accomplished, as shown in Fig.2b, by switching end 5 to bus 9 and end l to bus I0. To secure the nextlower value of inductance the windings are thrown into four groups eachhaving two windings in series. 'I'his is accomplished, as shown in Fig.2c, by switching ends 3, and 'I to bus 9, and ends 2' and i' tobus. I0.Tosecure the lowest value oi inductance all eight windings are placed inparallel. This is Y accomplished, as shown in Fig. 2d, by switchinglower end of the structure. then the switching may be accomplishedentirely at the lower end. A convenient structure for securing thisresult and mounting the switching mechanism, is shown in Figs. 3 and 4.The eight windings of Figs. 1 and 2 are wound upon a suitablethin-walled tube II of insulating material, core I2 being arranged toslidably enter tube II from the far end thereof. At either end of tubeII there are discs I3 and I4, also of insulating material, and runningbetween these discs, staked or otherwise suitably' fastened intoequi-angularly spaced lholes around the peripheries thereof are smallwire bus bars I" to 8" inclusive. The'ends I to 3' inclusive, oi theeight windings are soldered respectively to bus bars i" to 8" inclusiveand are thus returned to the opposite end of the form, where the busbars are terminated in suitable switch contact points. The ends I' to 8inclusive, of the eight windings are connected directly to eightswitch-points, also equi-angularly spaced, but at a smaller radius thanthe bus bars. It will be apparent that by bringing suitable sets ofswitch-arms into contact with switch-points I to 8 and I to 8, the fourdifferent connections of 'the windings explained in connection with Fig.2 can be secured, and switching of the associated capacitors can beaccomplished in the same switch-gear.

It will be noted that for all four inductance values each oftheswitch-points in Fig. 2 is connected either to an adjacent switch-pointor to one terminal of the complete coil. Thus switch-point 4' isconnected to switch-point 5 for position a of Fig. 2 and to bus bar I8(not shown in Figs. 3 and 4) for positions b, e and d of Fig. 2.Similarly, switch-points 2 and 8 are connected respectively toswitch-points 3 and 1 for positions a and b, and to bus bar III forpositions e and d. And finally, switch-points I', 3', 5' and 1' areconnected respectively to switch-points 2, 4, 8 and 8 for positions a, band c and to bus bar I for-position d. Switch-points 2 to 8, when notconnected to switch-points I to 1' respectively as just described, areconnected to bus bar 9.

Ou1 improved switching mechanism is illustrated in Figs. 6 and 'I to beemployed in combination with a coil structure such as that shown inFigs. 3 and 4 to secure the switching functions indicateddiagrammatically in Fig. 2. In Fig. 6, switch contact points 2 3 and I'1are arranged in seven radial pairs, spaced 45 degrees apart in the samemanner as in Fig. 4, upon a suitable disc of insulating material whichmay be cam slots 48-54 in ring 31. Contactors 45 are of such shape thatin the outward position of each arm, the inner contacter connectstogether the corresponding radial pair oi' switch contact points, whilethe outer contactor restsupon the ring 31. Upon moving the arm inwardly,the inner contactor connects the inner switch contact point to contactring 38, and the outer contacter connects the outer switch contact pointto the ring 31.

Ring 31 is rotatably supported in peripheral guides, not shown, and hasgear teeth around 45 degrees of its periphery, which engage a pinion 58mounted upon a shalt 51 to which an operating knob, not shown, may beattached. Arms 38--44 are restrained to radial motion in slots inupwardly projecting inner rim 58 of ring 36 and by similar slots inguide members 5S at their outer ends.

Cam slots 4Ii-54 are so shaped that upon rota- -tion of ring 31 throughsuccessive angles o! 11.25 the four diderent connections shown in Fig. 2oi' the eight windings of a coil such as shown in Fig. l areaccomplished. In the position shown in Figs. 6 and 7, the connectionscorrespond to those of Fig. 2a, all eight windings being connected lnseries. Cam slot 5i is of such shape that immadiately upon clockwiserotation of ring 31 arm 4I is moved inwardly to connect switch contactpoint 4 to ring 31 and switch contact point 5 to ring 38, to secure thearrangement oi Fig. 2b. Upon further rotation of ring 31, arm 4I remainsin its inward position and arms 39 and 43 are moved inwardly to securethe arrangement of Fig. 2c, Upon still further rotation of ring 31, arms39, 4I and 43 remain in their inward positions and arms 38, 40, 42 and44 are moved inwardly to secure the arrangement of Fig. 2d. Uponcounterclockwise rotation of ring 31 the reverse operations occur.Suitable notches and a pawl, not shown, may be provided to indicate thefour positions of ring 31, and to hold the,

ring in a selected position. A suitable stop, not shown, may be providedeitheron ring 31 or on shaft 51 to prevent rotation of ring 31 beyondits proper end positions.

Terminal I of the first winding is permanently connected to ring 38, andterminal 3' of the eighth winding is permanently connected to ring 31.The ungrounded terminals of condensers I8, I1, I8 and I3 oi' Fig. 5, arebrought to contact points 88, 8|, 82 and 83 respectively oi.' the switchin Fig. 6. Mounted upon ring 31 and rothe end disc I4 of the form shownin Figs. 3 and an inner switch contact point to the adjacent outerswitch contact point,A proceeding always in a clockwise direction (orvice versa) except for terminals I and 8' to be described later.Inwardly of the radial pairs of contact points, there is a contact ring38 corresponding to bus 8 of Fig. 2. Outwardly oi' the radial pairs ofswitch contact points, there is a ring 31, which corresponds to bus I 0of Fig. 2. Positioned over the switch contact points 4and the rings 38and 31 are seven radially movable arms 38-44 of insulating material. Inthe drawing, arms 38, 39 and 40 are broken away to -show the radialpairs of switch contact points. Each of these arms carries twocontactors, 45, which have pins 48 tating therewith vin a smallcontacter 84. As ring 31 is rotated to select a desired connection ofthe coil windings, contactor 84 moves over contacts SI1-83 to connectthe appropriate condenser 'into circuit, as explained in connection withFig. 5. For convenience in the drawings, ring 31 is shown radiallyoutside the switch contact points and in the same piane, but it mayalternatively be made of an outside diameter corresponding to the outercircle oi' switch contact points and may be positioned above them, bysuitable repositioning of the contactors 45 and the follower pins 41.

In the switch gear shown by way of illustrative example in Figs. 6 and'1, ring 31 acts as a rotary cam to actuate arms 38-44 and also as a busbar and electrical terminal of the compound coil.

If preferred, ring 31 may be made o! insulating material, and a separatering of suitable contact metal may be added to act as a b uscorresponding to bus I0 of Fig. 2. Numerous other modications will occurto those skilled in' the art.

in the higher frequency bands.

As is known, the inductance change produced by a particular core dependsupon the dimensions and proportions of the coil with which it is used,but is independent of the inductance value of the coil. Thus, using asingle core, the in- Yductance change and therefore the ratio ofmaxiquencies in each band will, in general, be greater This fact makesadvisable a compromise in the choice of the material from which the coreis made, so that the inductance-to-resistance of the circuit will bedecreased by the core only in the highest frequency band, or the twohighest frequency bands, will remain substantially constant in thesecond or third band, and will be increased in the fourth or lowestfrequency band. It is to be remembercd thatthe coil construction inaccordance with the invention provides exceptionally good qualitycoemcient, Q, on the higher frequency bands, so that while the change inQ over the frequency band is more pronounced in the higher frequencybands, nevertheless very satisfactory gain and selectivity can besecured in all bands.

Fig. 5 is a schematic diagram of a receiver embodying the invention, ofthe superheterodyne type, and employing a series-tuned antenna cir.

cuit and an oscillator circuit, 'followed by the usualoscillator-modulator, intermediate-frequency amplifier, detector,audio-frequency ampliier and loud speaker as indicated. Coils, andswitch-gear to accomplish the necessary inductance and capacitancechanges for the different frequency bands, of the type above describedare indicated by the blocks marked Antenna coil and switch andOscillator coil and switch. The antenna I5 is permanently connected toone terminal oi the antenna coil, the other terminal of the coil beingconnected to a grid of the oscillatormodulator tube. The antenna coilswitch automatically selects one ofthe condensers I6, l1, I8 or it forthe selected frequency band. The oscillator circuit is of conventionaltype, and as shown employs shunt coils and 2| and'series coils 22 and 23on the two lower frequency bands respectively, capacitors 24 and 25beingA connected permanently across shunt coil 20 and capacitorsv 25 and21 being permanently connected across shunt coil 2|. The proper completecombination of shunt coil, series coil, and capacitors is selected bythe coil switch. Similar shunt and series'coils may also be employed onthe two higher frequency bands. although they are usually not necessary.As shown, for the two higher frequency ranges, the oscillator circuitemploys capacitors' 23-29 and capacitors -31 respectively. The antennacoil switch and the oscillator coil switch arevmechanically con nectedfor simultaneous operation by means of a single knob, as indicated bythe dotted line 32. Ferromagnetic cores 33 and 34 are associated withthe antenna coil and the oscillator c'oil will occur to those skilled inthe art. For example, the arrangement according to the invention mayequally well be/ employed in parallel-tuned input circuits, and ineither the plate circuits or the grid circuits of tuned radio-frequencyamplifier stages. Additionally, as already noted, the arrangementaccording to the invention may be employed in receivers having less thanfour frequency bands, and in cases in 'which itis" preferred to employseparate coils permanently connected as above described.

In the detailed description of our invention we have chosen anarrangement for providing four frequency bands, since this example isadequate to illustrate the principles involved. it

will be understood, however, that the invention is not limited to amaximum of four frequency bands, and that it may be .applied to live ormore bands as may be required.

Having thus described our invention, what we claim is:

1. As a means for selectively connecting a plurality of permeabilitytuned inductance coils in differentones of series, parallel andseriesparallel arrangements, the combination of a mounting plate,concentric flat metal rings mounted on said plate and spaced from eachother radially by a substantial amount, pairs of electrical contacts forconnection with the terminals of said coils and each pair mounted onsaid plate between said rings and spaced therefrom and from each other,said rings constituting bus-connections for the selective connectingmeans, movable switch arms having conductive contactors for selectivelyconnecting said electrical contacts and said rings, and cam mechanismfor actuating said switch arms.

2. As a means for selectively connecting a plurality of permeabilitytuned inductance coils in different ones of series, parallel andseriesparallel arrangements, the combination of a mounting plate,mounted on said plate and spaced from each other radially by asubstantial amount, pairs of electrical contacts for connection with theterminals of said coils and each pairmounted on said plate between saidrings and spaced therefrom and from each other, said rings constitutingbus-connections for the selective connecting means, movable switch armshaving conductive contactors for selectively connecting said electricalcontacts and said rings, and cam i mechanism for actuating said switcharms, said switch arms being mounted on said plate in respectively andare arranged for movement in radial arrangement for longitudinalmovement and respectively in line with said pairs of contacts.

3. As a means for selectively connecting a pl rality -of permeabilitytuned induotance coils in different ones of series, parallel andlseries-parallel arrangements, the combination of a mounting plate,concentric flat metal rings mounted on said plate and spaced from eachother radiallyY by a substantial amount, pairs of electrical contactsfor connection with the terminals of said coils and each pair mounted onsaid plate between said rings and spaced therefrom and from each other,said rings constituting bus-connections for the selective connectingmeans, movable switch arms having conductive contactors for selectivelyVconnecting said electrical contacts and said rings, and cam mechanism'for actuating 'said switch arms, said switch arms being of insulatingmaterial and each of said cntactors .being adapted to electricallyconnect concentric fiat metal rings tween said rings and spacedtherefrom and from each other, said rings constituting bus-connectionsfor the selective connecting means, movable switch arms havingconductive contactors for selectively connecting said electricalcontacts and said rings, and cam mechanism for actuating said switcharms, each pair of said contacts cooperating with one of said switcharms and constituting terminal connections one for 10 each to two ofsaid coils.

WILLIAM A. SCHAPER. GEORGE B. MCCLELLAN.

